Homogeneously Dispersed and Chemically Couple-Linked MXene-PEO Composite Polymer Electrolyte Membrane for All-Solid-State Lithium Metal Batteries
Yonghong Wang, Xuejiao Chen, Weike Zhao, Qijun Yu, Qiuhua Zhang, Yuanhang Zhou, Junwu Liu, Xianjun Xing, Yonglong Zhang
Abstract
The comprehensive properties of inorganic–organic nanocomposite polymer electrolytes (CPEs) are significantly blocked due to their inherent poor interface compatibility, even though they have good mechanical and electrochemical properties. Herein, conceptional ideas on the molecular bridge design and interface engineering strategy of materials were put forward using organic silane compounds with chemical couple-linked groups, i.e., γ-(2,3-epoxy-propoxy-propyl) propyl trimethoxysilane, to form strong chemical interactions between the polymer matrix and the 2D nanoinorganic filler (MXenes, Ti 3 C 2 T x ) . These allow homogeneous dispersion of MXenes into the polymer matrix and build up rapid ion-transport pathways. Furthermore, the abundant negative charge groups on the functionalization surface of MXenes can effectively repel the anions of LiTFSI salt and attract Li + in CPEs, thereby regulating charge distribution at the electrolyte-anode interface and promoting uniform deposition of lithium atoms. The as-prepared CPE membrane exhibits an impressive ionic conductivity of 5.6 × 10 –4 S·cm –1 and a high Li + transference number of 0.41 with an extended electrochemical window (5.0 V vs Li + /Li) at 60 °C. Benefiting from the homogeneous dispersion of MXene fillers and the robust chemical coupling linkage interaction, the growth of lithium dendrites is effectively inhibited, enabling stable lithium deposition/stripping processes at low polarization voltages. At a rate equivalent to 0.1 C, the first cycle discharge capacity reaches up to 168 mAh·g –1, and the assembling full cell LiFePO 4 ||CPEs||Li presents improved cycle stability with a capacity retention of 93.8% after 200 cycles at the rate of 0.5 C. This work not only broadens the application field of nanosheet MXenes but also provides a new strategy for the design of nanocomposite solid polymer electrolyte membranes for lithium metal batteries.